Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $67.31   5.768%   $71.1924   $71.19   $71.20   $71.20  
  Purchase #2 $227.86   4.670%   $238.5011   $238.50   $238.50   $238.50  
  Purchase #3 $206.99   8.104%   $223.7645   $223.76   $223.75   $223.80  
  Purchase #4 $63.70   9.535%   $69.7738   $69.77   $69.75   $69.80  
  Purchase #5 $154.78   3.409%   $160.0565   $160.06   $160.05   $160.10  
  Purchase #6 $61.49   6.655%   $65.5822   $65.58   $65.60   $65.60  
  Purchase #7 $193.58   11.581%   $215.9985   $216.00   $216.00   $216.00  
  7 purchase totals = $975.71       $1,044.8690   $1,044.86   $1,044.85   $1,045.00